Quantum‒Chemical Simulation of Molecular Hydrogen Abstraction from Magnesium Borohydride Diammoniate

Within the framework of the cluster approach using the 6‒31G* basis set and the hybrid density functional (B3LYP), we modeled successive abstraction of H2 from the complexes (Mg(BH4)2∙2NH3)2 and (Mg(BH4)2∙2NH3)4. It was found that the initial stage of dehydrogenation needs overcoming energy barriers ~ 1.5‒1.2 eV, which requires preheating, then the process can go on with energy release until about 10 wt % of H2 is extracted, for a higher degree of conversion, additional energy costs exceeding the combustion heat of H2 will be required when extracting more than 12.5 wt % of H2. Therefore, further dehydrogenation of this compound may turn out to be inexpedient from the energy point of view.